When providing Asynchronous Transfer Mode (ATM) access on a communication switch or router capable of sophisticated Layer 3 communication traffic management, as is often the case in communication systems, it is generally desirable to allow outgoing customer communication traffic to be subject to communication traffic management at both Layer 3, typically Internet Protocol (IP), and Layer 2 (ATM). In other words, a service provider may wish to shape or rate limit different classes of IP traffic separately, and then shape the aggregate flow in conformance with an ATM traffic descriptor.
However, ATM traffic management is typically provided through specialized hardware that is also responsible for cell segmentation and reassembly, while IP traffic management may use the same hardware as is used for other access technologies at a switch or router. Relatively generic and costly hardware which supports various technologies such as IP may therefore be provided in multiple circuit card slots of a switch or router. Any of a variety of types of less costly medium- or protocol-specific access technology modules such as line cards are then connected to the generic hardware to provide an interface to a lower layer protocol for each circuit card slot. The same routing hardware may thus be used with different access technology modules.
In advanced communication switches or routers, communication traffic management at both Layer 3 (L3), to enable different communication traffic handling for different Differentiated Service Code Point (DSCP) codepoints for instance, and Layer 2 (L2), such as shaping in conformance with an ATM traffic descriptor, may be achieved through the use of specialized hardware that combines L3 and L2 communication traffic management in either a single communication device or a small number of devices that were designed to work together.
When budget, time-to-market, or other constraints preclude the creation of specialized hardware, it may be necessary to combine L3 and L2 communication devices which were not designed to work together. In this type of implementation, each traffic management device normally discards communication traffic as queues exceed configured thresholds or if buffer pool exhaustion, indicative of high total queue occupancy, occurs. In the above example of L3 and ATM traffic management, the ATM traffic management device would discard communication traffic as its per-VC queues fill up. These discards are not L3 class-aware, with communication traffic of any particular L3 class just as likely to be discarded as communication traffic of any other L3 class, thereby effectively defeating the L3 traffic management.
Accordingly, it may be desirable to provide a communication traffic management mechanism which allows the use of different traffic management devices to accomplish complex traffic management without using specialized hardware. Even where such a mechanism is provided, there remains a need for monitoring the effects of the traffic management mechanism. This allows a determination to be made as to whether traffic management is actually achieving desired behaviors.